Two longtime Clinton donors, Sandy Robertson and Susie Tompkins Buell, will host a high-dollar fundraiser in San Francisco next week for "Ready for Hillary," the leading super PAC supporting a second Hillary Clinton bid for the White House.

Buell, a major Democratic donor and a close friend of the former secretary of state, serves as a co-chair of the PAC's national finance council. She will co-host the fundraiser at Robertson's home in San Francisco on Monday, Nov. 4, according to two sources with direct knowledge of the event.

Tickets will run at $25,000 each — the amount at which donations to the PAC are capped, according to a policy the group voluntarily established to emphasize low-dollar donations. Craig Smith, a senior advisor to the PAC who has traveled in recent weeks to New York and Tampa on behalf of the group, will speak at the event.

Ready for Hillary, which has been list-building and harnessing grassroots support for Clinton's non-candidacy since January, has ramped up its fundraising efforts in recent weeks. It announced last week that billionaire George Soros will join Buell as a finance co-chair ahead of the council's first meeting on Nov. 12.

The group has said that 97% of its contributions are in the amount of $100 or less, but the Robertson-Buell gathering will be one of its highest-dollar events to date.

Another fundraiser, scheduled in Los Angeles on Nov. 6, is more typical of the PAC's events — the suggested ticket price is $20.16.

Robertson, the founding partner of a leading tech-focused private equity firm, was one of Bill Clinton's earliest fundraisers, backing his run for president in 1992, but supported then-Senator Obama over Hillary Clinton in 2008. Both Buell and Robertson have each made individual contributions of $25,000 to the group, according to filings with the Federal Election Committee.

Robertson joins a growing outfit of early Obama supporters, like Sen. Claire McCaskill, who have found in the PAC a venue to voice their support this time around for Clinton before she even announces a campaign.

Ruby Cramer is a politics reporter for BuzzFeed News and is based in New York.